It has often been proposed to use infrared cameras to produce images of a roadway revealing warm objects such as humans, animals or other sources of infrared radiation. This has the advantage of detecting such objects at night particularly if they are beyond the range of vehicle lights. Such systems have typically used a video monitor or the like to display the detected objects. A traditional monitor is bulky and difficult to locate in a convenient place for viewing, and requires the operator to look away from the roadway to observe the infrared image. The image would be quite small relative to the real roadway scene so that there could be some difficulty in accurately judging the distances of the objects being displayed. Thus if an object is not visible in the real scene, it is hard to determine its location.
It is also known to employ head up display techniques to project instrument images or vehicle parameter data onto the vehicle windshield or other combiner so that the display is in or immediately adjacent to the operator's line of sight. Such displays have been quite small relative to the roadway scene due to the limited space available for the required image source and projection mirrors.